Conventionally, a coil forming a rotor of a small coreless motor must be shaped with a high degree of precision. A method of winding a cylindrical coil by successively winding a wire material diagonally around an outer periphery of a core may be employed as a method of manufacturing this type of coil. A winding apparatus used with this method includes a nozzle that rotates relative to the core while feeding out the wire material, a wire retainer that guides the wire material wound around the core to a predetermined position of the core, and a core rotating mechanism that rotates the core relative to the wire retainer.
In JP3588586B, the present applicant proposed a winding apparatus and a winding method for leading a wire material wound around a wire retainer smoothly to an outer peripheral surface of a core by inclining a locus of a nozzle that rotates relative to the core relative to a center line of the core and, during a process in which the wire retainer guides the wire material to the core, varying a contact angle of the wire retainer relative to the core while keeping the wire retainer in contact with the core.
With this winding apparatus and winding method, the contact angle of the wire retainer relative to the core is varied while keeping the wire retainer in contact with the outer periphery of the core, and therefore the wire material wound around the wire retainer can be encouraged to slide down the surface of the wire retainer and move onto the core. As a result, the wire material is wound around the core in a predetermined position. Thus, winding irregularities in the successively wound wire material such as overlapping and gaps can be prevented.